Material for receiving inscriptions and method of making



Nov. 13, 1962 D. P. NORMAN 3,063,364

MATERIAL FOR RECEIVING INSCRIPTIONS AND METHOD OF MAKING Filed Sept. 28,1959 2 Sheets-Sheet 1 FIGI DANIEL P NQRM, rfu 5??- ATTORN EYS Nov. 13,1962 D. P. NORMAN 3,063,864

MATERIAL FOR RECEIVING INSCRIPTIONS AND METHOD OF MAKING Filed Sept. 28,1959 2 Sheets-Sheet 2 United States Patent Ofiice Ipswich, Mass,assignor to Ipswich Ipswich, Mass, a corporation of Massa- Thisinvention relates to a medium in the nature of a sheet of paper forreceiving inscriptions of significant symbols or representations, forinstance in the form of lines, and to a method of producing the same.The nature of the product is such that it probably will be most helpfulto introduce the description and later explain the details more or lessmetaphorically and with liberal use of analogies to well known thingswhich are in fact substantially different. It may be said however thatthe product is a sheet of generally uniform appearance and tone ofcolor, like a blank sheet of paper on which is produced an inscription,generally in a contrasting color, by the action of an inscribinginstrumentality which may be similar to and operated generally as a pen,pencil or raised piece of type is used on paper, without however thetransfer of any ink, pigment or the like to produce the inscription. Theinscription may arise from pressure of the instrumentality, from heattransmitted therefrom (or heat and pressure combined) or from thetraction of the instrumentality traversing the surface.

The product of the invention may be usefully employed for many purposes.When used under some ordinary sheet of paper or the like it will yieldduplicate copies similar to so-called carbon copies, although no carbonsare used, provided the original inscription is done by aninstrumentality which would produce a carbon copy. Thus the type of atypewriter or the pressure of a lead pencil or of a ballpoint pen or aso-called style-graphic pen would make an original on an ordinary sheetof paper, and identical copies on underlying sheets of paper embodyingthe invention. Stamping, as with a metal die of a time stamp or an inkedrubber stamp on the original would also be reproduced. Moreover, both anoriginal and copies as above described could be produced by operatingthe typewriter without any ribbon or writing with a dry stylus forinstance, or a ballpoint pen which no longer has any ink in it. Sincethe writing would immediately appear the act of manual inscription wouldbe as easy and natural as doing it with a pen or pencil. What has beensaid applies to all types of multicopy business forms such as salesslips, autographic register supplies and so on, wherein interleavedsheets of carbon paper are customarily used.

The paper will not only record the successive typing of letters in atypewriter, but will be affected by the pressure of raised type of aprinting plate or form of movable type without any ink being applied tothe type. For the production of small runs of work and for theproduction of books and magazines of ephemeral interest, the use of thematerial as stock might be advantageous where such printing mechanism isavailable, since such use would avoid filling and caring for inkingmechanisms and the cleaning up job afterwards. In many instances anumber of copies of satisfactory quality might be prepared from a singleimpression of the type form or plate, just as a number of copies couldbe simultaneously prepared in a typewriter by a single writing, andprovide an increased output as compared with the normal operations ofsimpler types of printing presses, in particular those of the bed andplaten type.

The product provides a useful chart, of circular or strip form for usewith all types of measuring instruments wherein the measurement istranslated into or indi- 3,063,864 Patented Nov. 13, 1962 cated by amovement of some part so that the amount of movement indicates in somemanner the value of the variable being measured. It is adaptable both toa linear inscription or one formed by dots.

Since the product operates because of a relationship of its componentelements which exists on a very small scale relative to the dimension ofthe inscribing instrumentality and which may approach the microscopic,or be, in fact, microscopic, it is necessary to illustrate the followingdescription by diagrammatic drawings on an enormously exaggerated scaleand to express their relationship by words naturally used and understoodwith respect to coarser and macroscopical relationships more familiar toordinary experience, but which it is believed will be suggestive andpromote a ready understanding, although they may not carry all theconnotations of their commoner usage.

The following specification is illustrated by drawings wherein:

FIG. 1 is a mere graphical memorandum illustrating the production of aninscription on a base sheet by a stylus-like instrument;

FIG. 2 is a diagrammatic plan view of an exemplary form of the inventionon an enormously exaggerated scale, as indicated by certain dimensionsindicated thereon;

FIG. 3 is a diagrammatic section on line 33 of FIG.

FIGS. 4 and 5 are diagrams similar to FIG. 2 showing modifications; and

FIG. 6 is a diagrammatic illustration of a rotary intaglio (gravure)printing press such as may be used in manufacturing the product.

In FIG. 1 I illustrate a partially unrolled scroll S on which we seeinscribed a line G which has been formed by the action on the surface ofan inscribing instrumentality I in the nature of a stylus which hasmoved from above along the line G to the position shown. In the usualcase of manual inscriptions on ordinary paper such a stylus would be apen with ink or a lead pencil, in each case transferring markingmaterial to the surface of the inscription receiving medium. Similarinscriptions are made in various types of recording mechanisms, such forexample as a recording thermometer or thermograph, by pens or by styliwhich scrape away the surface of the chart, or which by means of heat orpressure, or both, locally displace or melt a coating on the chart toreveal the contrasting color of its backing. The material contemplatedby the invention might serve as such a scroll or chart and be inscribedby a stylus although having a more extensive application as willhereinafter be noted. I believe however that it will facilitateunderstanding if I describe it first in connection with such a stylusinscription, as I shall now do without limiting intention. It should beunderstood that no ink is used, nor is any functionally equivalentmaterial transferred by the stylus to the record surface.

In accordance with the embodiment of the invention referred to I wouldusually utilize a base of paper or similar thin sheet material such asmetal foil or a film of polyethylene terephthalate (known by the tradedesignation Mylar) although the use of rigid bases is not excluded. Thisbase serves as a carrier for the medium by means of which theinscription is formed and recorded thereon, but is inert to thestylus-induced changes in that medium by which the inscription isbrought into existence. The desirable qualities to be considered inchoosing the base will be obvious to those skilled in the graphic arts.On this base is a coating which to the naked eye is of a uniformcharacter and of apparently uniform color or tone. When a positiveinscription is desired the base will. be of a relatively light tone tocontrast with an inscription of darker color. Microscopically howeverthis coating is not continuous. This does not mean merely that amicroscope can identify individual particles existing in an apparentlycontinuous film. The coating consists of minute areas, tiny dots (FIG.4) or streaks like the filament of a spiders web (FIG. which are veryclose one to another but yet are separate as isolated individualentities in a geometrical pattern over the area of the backing. Ibelieve that to say that adjacent ones have an airgap between them willbe a concept helpful to understanding. These isolated areas of coursehave dimensions and a volume, but so small that many common wordsdefining those properties would be misleading to the ordinary reader. 1shall therefore term them quantula to avoid misleading connotations.

In FIG. 2 I have shown a preferred form of product wherein a carrier hason its surface quantula 12 and 14, specifically different as regards thematerials thereof. The dimensions marked thereon are typical. Outlinesare diagrammatic only. The altitude (perpendicular to the plane of thepaper viewing HG. 2) will generally be less than two-thousandths of aninch. It will be helpful to observe that the end of a commonly usedballpoint pen, which is a stylus making a rather fine line of depositedink, is of such width that it would span the entire group of quantulashown in this figure and engage all of them. In printers measure thewidth of the group is about two points, and the area only aboutone-thirtieth that of one pica em quad. The entire group shown could bereceived within a square with sides one-sixteenth of an inch long withroom to spare. In general the invention contemplates that severalquantula of each kind will be received in such an area.

The megascopically uniform appearance of the coating may be understoodby another analogy. It is well known that a half-tone pitcure is anassemblage of minute dots of ink in various densities of distribution inthe various lights and shades of the picture. In a coarse halftone in anewspaper even the unaided eye may apprehend that fact. In a bettergrade half-tone it may appear on inspection with a lower powermagnifying glass. The attempt to discern details of the orignal objectrepresented in a half-tone by use of a magnifier will usually beunsuccessful. We then see the trees but not the forest, the dots but notthe outline of the object represented. In a superior half-one the solidblacks of the original so appear to the naked eye in the reproduction.From a high flying airplane a green lawn, even a green forest, appearsas a solid green surface.

The use of two numerals 12 and 14 in FIGS. 2, 4 and 5 and thecontrasting lining on the areas so designated disclose that the coatingcomprises quantula of two different kinds (there will be at least two).The materials in the quantula 12 and 14 are reactants which on mixinggive rise to a conspicuous difference in appearance in the area ofmixing. The expression reactants" usually will signify a reaction in thechemical or physico-chemical sense. The change in appearance willordinarily be a difference in color and may be termed a chromogeneticreaction or change. The two kinds of quantula are present inco-substantial numbers, that is, they may not be equal in number for agiven area, or collectively of equal area or equal volume or equalweight, but in these respects one will not be only a very small fractionof the other.

In FIG. 5 there are shown reactants applied in alternation as narrowlongitudinal stripes or streaks (in fact hair like) along the carrier.In FIG. 4 these stripes become a series of dots. In a preferred formshown in FIG. 2, (one presenting decided advantages in manufacture aswill appear) the quantula form a quincunx or staggered pattern theelements of adjacent vertical files being offset and desirablyoverlapping as shown. Herein the elements of each file carry the samereactant. However, if we draw lines at 45, we perceive ranks and fileswith alternate elements different and a migration of material across theintervening air gaps initiated by a diagonal component of movement wouldbe particularly effective in mixing the reactants.

Let us consider the elfect of drawing a stylus as diagrammed in FIG. 1with light pressure across a sheet as shown in FIG. 2. It should beborne in mind that the end of the stylus is broad relatively to the sizeof the quantula and the air gaps between them. An ordinary penpoint isas wide as the area delineated in FIG. 2.- Here again an approach byanalogy may be useful. If ink has been spattered on a desk and appearsthereon as little separate drops, if we draw a small brush (a pencil)-across the area we will brush out a series of the drop-- lets into aline. If we have thrown down shovelfuls of earth one after another inclosely spaced relation along our garden bed, and then draw a rake alongthe row, the little mounds are merged and mixed. So the stylus mergesand mixes the quantula in its path, causing at least one of thematerials therein to move across the separating gaps which relativelyisolate them and the materials react with a resultant conspicuous changeof appearance which delineates the path and constitutes an inscription.If, in the case of spattered ink we had pressed down our thumb, we wouldhave pushed together the droplets beneath it to produce a smudge ofconsiderable area. Similarly if we press a raised type face on theinscription medium it will crush the quantula beneath it and pushtogether the materials therein or permit their flow to mix with oneanother.

The quantula have previously been referred to as close one to anotheryet isolated. Isolated obviously means that there is such a spacebetween adjacent ones that the reactant material in one will notinfluence that in another. The distance need not be great, a miss hereis as good as a mile, but it is real. By close is meant that theintervening spaces should not be so wide, having regard to the volumesof materials involved and their physical state when the inscription isbeing made, as to prevent mixing by movement of material across thegaps. The distances involved are always small, although percentage-wisethere might be considerable variation. Perhaps it could be said that theideal would be to is consistent with efiective isolation under theconditions of storage and handling. The dimensions marked on FIG. 2 byway of example represent one adequate approximation to this ideal andone susceptible of attainment by such procedures and mechanisms as laterdescribed.

While theoretically the chromogenetic or other reaction arising from theadmixing of different quantula might be a solid phase reaction, aprompter and more pronounced effect will occur if one at least is liquidat the time of mixing. The occurrence of a reaction will of course beinfluenced by the environment, the conditions of heat, pressure,humidity, etc., at the place of use and those due to the particularinscribing method used. Thus a heated stylus or a concentrated beam ofradiant heat might melt one material or the mixture of tWo solids mightmelt more easily than either alone, and thus react. The reactionshowever would not strictly be solid phase reactions. In cases ofrecording measuring instruments where the inscription would be a curveshowing the changes of a variable condition, the tracer movingresponsively to such changes might release locally to the inscriptionmedium some product of the process being observed which would be potentto initiate the reaction between adjacent quantula over which the tracermoved.

Since the dots are over the uninscribed medium there is no contrast andthe megascopic impression would be one of uniformity. Psychologically itis recognized as an approximate rule of thumb that a series of discretedots to an inch represents the dividing point at which the average eyewill no longer differentiate between discrete dots and a continuous lineor 100 x 100 to the square inch, a continuous film. A substantiallylower number will be apprehended as dots and a substantially highernumber as a continuous line or surface. Provided the size and spacing ofthe dots are so. related to make the spaces as small as the inscribinginstrumentality as above explained, an inscription will be produced. Forsome applications a perceptible dot pattern in the inscription isacceptable, just as a medium screen half-tone might be. The closerspacing of a finer dot pattern would produce a better qualityinscription.

Conveniently the material when viewed by the naked eye is substantiallywhite, but may be of a suitable color. Thus in manifolding differentcolors for the different copies are desirable. This does not mean thatsome of the reactants in themselves or one array of quantula may not bedark colored. The analogy of textile fabrics, wherein a judiciousmixture of White yarns with dark will give an overall gray effectwithout any conspicuous stripe or pattern, may be recalled. The finesubdivision involved also tends to make the appearance lighter thansimilar material in massy form.

A quantulum as 12 comprising a solid reactant may in certain cases beformulated by melting the reactant or dissolving it in a comon solventto produce a fluid or semi-fluid which may be printed onto the carriermuch as ink is printed and which, when set, will adhere. Otherwise itmay be produced by dispersing the material in very finely divided solidform in a fluid suspending medium, molten or a solution, quantula ofwhich may be applied at proper spaced relationship to the carrier anddried, the continuous phase of the suspension medium then forming abinder securing the solid particles. The physical relationship of thecomponents will be comparable to the suspension of solid pigments in afluid in the case of a printing ink.

Liquid bearing quantula may be deposited as a dispersion of minuteliquid droplets (marked 14a in FIG. 2) in a suspending medium. The fluidmixture will be an emulsion. The dispersion produced from such anemulsion by setting of the external phase is also sometimes termed anemulsion, but that usage is inexact. An encapsulating medium may beincluded which encloses each droplet in a shell and such a shell willpersist in the dispersion. Rupture of the shell will release the liquid.

There has been discussed a system comprising two arrays of quantula,respectively of diiferent material. Thus one set representing onematerial might be arrayed in rank and file and the other similarlyarrayed, but with its elements out of register with those of the other,so that the elements of the two are interspersed, but individually eachof the elements is isolated from all the others. Clearly there might bemore than two arrays, say each different from both the others. Thematerials of three such arrays might be inert to one another pairwise,but when brought together all three give rise to a reac tion useful forthe purposes. Similarly in a two array system, two of such threematerials might be in one array and the third in the other. One of thetwo materials might be a catalyst promoting the reaction between theothers, or it might serve as a flux when the inscribing involvessubstantial added heat. In some cases the production of a gas might bethe first stage following mixture and the gas enter into a secondaryreaction to pro duce the significant change. The generation of a gas asa by-product of such a change, the gas simply being dissipated, would beunusual, but conceivable.

The inscribing medium should withstand reasonable handling. Thus itshould not smudge by ordinary contact with the fingers or by the rollsof a typewriter if such a machine is used for inscribing. The contactsinvolved in those cases are over such relatively huge areas compared tothe size of the quantula or the effective areas of a stylus point or acharacter of raised type. The prodnot should also not deteriorate,become fogged, if piled up in sheets or rolled up in successiveconvolutions. In other words it should have a good shelf life. To ensurethis it is preferred to make the solid phase quantula 12 of greateraltitude than the more frangible liquidbearing quantula 14 asillustrated diagrammatically in FIG. 3. Their tops Will then take thepressure and contact with the tops of liquid-bearing quantula isavoided. The pressure here referred to is distributed over a large areaand supported by multitudinous surfaces of the greater height. Thedifference in height may and should be small so that the stylus appliedin a small area will not skip from one height to another and miss anintervening liquid-bearing quantulum of lower elevation.

It may be worth while to point out that the quantula would in practiceprobably not have so regular 21 form as is shown in diagrammatic FIGS. 2and 3. They would be initially shaped by the mechanism used in applyingthem and forces of surface tension would tend to produce more or lessspherical or ellipsoidal shapes. However an attempt to show shape inthese figures would not be realistic either and the pretence is avoided.

For preparing the product described, suitably selected stencilling orprinting techniques may be adopted and adapted. In general the quantulawill be supplied in a fluid or semi-fluid state analogous to the inks inthe conventional operations of the processes in question.

For small production runs or for testing purposes stencilling isavailable utilizing the methods and techniques of the silk screenprocess.

More generally the work may be performed by an intaglio printing pressor a suitable modification thereof, no inks being used of course. Thereactants are prepared as a fluid or semi-fluid form analogous in thatproperty to ordinary inks and having due regard to the nature of thebase sheet to which they are applied, and are handled in general as areordinary inks.

By intaglio reference is made to a printing surface (plate or cylinder)in which are formed depressions corresponding to the design to beprinted, which are filled with ink after which the original even surfaceis wiped clean. The surface is presented to the paper with lightpressure and the ink is picked up by the paper from the depressions. Thecylinders or plates of a press of this general type are usually operatedso that the ink on the paper will spread beyond the area of thedepression and merge with that of some adjacent depression. In the present instance that will not be the case.

While die-stamping and flat-bed printing from intaglio surfaces might beused, for economic reasons a rotary printing cylinder would probably beused commercially and the machine employed would be a multicouple,rotary, intaglio, sheet or web press. FIG. 6 is a diagrammaticrepresentation of a web press.

The succeeding paragraphs are limited in expression to a two arraysystem of quantula, each array being formed of individual quantularelatively spaced in a geometrical arrangement and the two combined withthe elements in each relatively spaced from those in the other. Thus inFIG. 5 alternate vertical stripes constitute one array of parallelstripes and the intervening one the companion array, as indicated by theuse of separate reference numerals 12 and 14. The reactants in therespective arrays are different. In FIG. 4 a series of separate smallareas replaces each stripe and those of one kind constituting one arraymight be considered as arranged in rank and file, while those of theother array are likewise so arranged, but with the ranks and filesoffset relatively to those of the first array. In this particulararrangement, as has already been pointed out, there are diagonalextending rows alternate elements of which are diverse. The Width of thetwo systems need not be the same. It is possible to have the solid arraywider than the liquid dispersion array to support more of the total(storage) pressure of the weight of flat paper on paper. I

In practicing the invention I may first imprint stripes 12 in the caseof FIG. 5, or areas 12 in the case of FIGS. 2 and 4 and cause theimpressions to dry or set and then, as by a second cylinder, imprintstripes 14 or areas 14 in the intervening spaces and in spaced relationto the former or, to use the printers term, in proper register,

having in mind the result to be produced. Patterns of the desireddelicacy and accuracy may be produced on the metal rolls by chemicaletching, in particular by the procedure known as inverted half-tonescreening, or by mechanical engraving as on a jewelers lathe. In chemical etching I prefer, but am not restricted, to the type of. cell knownas an inverted half-tone, with less than 50% tone, i.e., with the cellwalls not quite touching.

In general the array of quantula 12 which do not contain liquid shouldbe printed first. If the liquid containing. quantula were first printedthey might be crushed by the smooth outer surface of the succeedingcouple and the liquid would be released. This may seem inconsistent withthe recommendation previously given that the solid ones be of greateraltitude than the liquid-containing ones and it might be asked how theliquid-containing ones could reach the web. However the pressure of thesecond couple comes from a roll of elastic material and is exerted onlyin a narrow zone transverse of the path of the paper. The solid depositswhen set are of such compressibility and have such elastic recovery asto permit the liquid-containing ones, which are fiuid when printed andmay then be of greater depth when dry, to be subsequently applied to thepaper without objectionable spreading or shortening of the previouslyapplied solid ones.

In providing for accuracy of the register it is proper to considervariations in the area of the paper during the printing operation andvariations in the functioning of the mechanical elements of the press.

FIG. 6 is a schematic representation of a form of rotary multi-coupleintaglio press of the type such as might be used for preparing theproduct of the invention. In describing this I shall in the nextparagraph use the word ink as the one most readily understood when thedescription relates to a press, but it will be understood that it reallymeans the fiuid or semi-fluid mixtures previously referred to which ondrying form the potentially reactive quantula. The web W is led from theleft, as indicated by the arrow, from a suitable source of supply andthrough any conventional or suitable web conditioning means used in theart. Preferably it may be passed through a first nonprinting couplecomprising a hard surface, smooth roll 20 in size similar to theengraved rolls which will thereafter do the printing and moving at likespeed, and a cooperating impression roll 22 similar to the impressionroll of the following printing couples, the two rolls being urgedtogether to provide the same pressure as those printingcouples. Thepurpose of this couple will hereinafter be explained.

The web then advances to the first printing couple, com prising anengraved roll 24 taking ink from an inking supply 26 with which rollcooperates the doctor blade 28 which cleans off the surface of the roll,leaving the ink in thesunken portions, and the web then passes beneaththe impression roll 30 whereby ink is transferred from the depressionsof the etched roll to the paper. The web then continues over supportingrolls 32opposite a drying mechanism 34 (schematically shown) to set theink and then passes to a second couple like the one just described, pastanother dryer, and goes at the right of the figure to the rewinding orsheeting mechanism.

In good quality presses of this kind as presently manufactured it ispossible to feed ordinary webs through under a substantially constanttension. It is possible to control the so-called side to side registeralong the web within very close limits, say half a thousandth of aninch. The control of fore and aft or linear registration is not so goodmore particularly because the diameters of successive cylinders canhardly be made exactly equal. The web is subject to dimensional changesdue to changes in temperature, pressure and humidity. In the case ofpaper which has a decided grain, these changes are primarilylongitudinal.

The control of the consistency of the inks and the .8 pressure of thecouples is a matter within the skill of an able pressman.

The purpose of thefirst couple diagrammed is to apply initially to theweb before printing .lthe amount of pressure which it will encounter inpassing through the printing couples, so that its area will be asinvariable as possible during the succeeding printing operation.

By referring to FIG. 5 which shows the quantula applied in longitudinalstreaks, the elements of the different areas alternating, and to FIGS. 2and 4 wherein the quantula are arranged in rank and file and each file(vertical in the figures) is formed by quantula of the same composition,it is clear that unintended mixing of the quantula, due to inaccuraciesin the printing process, will arise from variations in the side to sideregister, and therefore arrangements of this kind are recommended asthis control is well within the capacity of precision gravure presses aspresently known.

In the case of the streaked or striated form shown in FIG. 5, inpractice, instead of having completely annular grooves etched in theprinting cylinder, it may be convenient to interrupt them at intervalsto provide shoulders cooperating with the doctor blade as the cylinderturns in such manner that excess material will be removed by the doctorblade, but only excess material, the grooves remaining full. Thesepartitionings need not be aligned in adjacent grooves, and they may befairly widely spaced. It will be seen, however, that if the stripes ofFIG. 5 are interrupted at intervals the construction will tend toapproach the construction of FIG. 4, although the individual depoaitsmay be much longer lengthwise of the web.

A number of exemplary formulations follow.

ExamplesGr0up I In the preferred formulations, the solid phase isapplied as a dispersion in a solvent-soluble binder, while the liquiddispersion is applied as an emulsion in a hot melt. In the followinggroup of examples, the solid reactant consisted of 10 parts ofbrom-thymol blue ball milled in parts of a solution of a film-formingbinder containing 15 parts of resin and enough solvent to produce aviscosity of between and 60 seconds, at 20 C., as measured by a No. 2Zahn Cup, except for the screen printing operation, where the solventwas allowed to evaporate until the ink had a paste-like viscosity. Theresin and solvent combinations were:

Dow Standard Ethylcellulose, 10 cps. (viscosity determined in an 8020toluene ethanol mixture), with the solvent medium toluene and isopropylalcohol.

Rohm & Haas Acryloid B82 (a commercial name for a polymer of esters ofacrylic and methacrylic acids) in toluene.

Nitrocellulose RS /2 second, a nitrocellulose ester made i by HerculesPowder Co. Solvent toluene.

Note that the Ethocel has also been applied from iso propyl and butylalcohol solutions. There is no limitation as to the nature of thesolvent used except that set by the solubility of the binder. Where thesolvents evaporate too fast (as in the case of a sheet-fed intaglioplate press) slower evaporating solvents such as xylene or butyl alcoholwill be used, as is the custom in ink formulations. In general, I havenot found it necessary to use a plasticizer in the binder, butconventional plastici zers can be used freely if a more flexible binderis wanted.

The alkaline, hot melt liquid reactant of the preceding example alsoreacts well with a solid reactant consisting of a ball-milled dispersionof 9 This pair of reactants is colorless, and turns pink when the liquidis broken.

The solid reactants have all been applied as dispersions, prepared byball milling the solid reagent in a solution of the resin (usually ballmilled 16 hours), and then adjusting the viscosity of the dispersion tothe desired printing viscosity. On a conventional gravure press theviscosity range of 60 to 120 seconds prints well-on an intaglio platepress, a viscosity of up to 180 seconds can be used.

The liquid dispersion was together:

100 parts of Cumar V-l (a coumarone-indene resin manufactured by theBarrett Division of Allied Chemical & Dye Corporation) having asoftening point of 110 C. are melted together with 20 parts of U.S.P.white prepared by premelting mineral oil, 0.5 part of igepal CA-630 (asurface active agent of the nonionic alkyl phenoxy polyoxyethyleneethanol type, manufactured by Antara Chemical Divis.un of GeneralDyestuff Corporation) and heated to 120 C. A separate solution of 27parts anhydrous potassium carbonate was dissolved in 86 parts of ethylene glycol, heated to 120 C., and was dispersed in the hotcoumarone-indene solution, using a high-speed turbine-type colloid millto achieve good dispersion. The colloid mill is conveniently preheatedto 120 C., in an oil bath. The emulsion or dispersion formed is of thewater-in-oil type, i.e., the ethylene glycol droplets form adiscontinuous phase completely surrounded by a continuous phase of thecoumarone-indene resin. This dispersion is applied on a press at atemperature of 115l20 C., using a heated plate or roll and a heated inkfountain.

Nora-10 parts of calcium oleate may be used in stead of the Igepal as asurface-active agent. Many other suitable surfactants are available.

The pairs of solid dispersions e.g., ball'milled bromthymol blue in abinder and the hot-melt dispersion of alkaline ethylene glycol wereapplied to a 16 lb. white bond paper by five difierent procedures.

A. On an engravers plate press, using a photoengraved chrome-platedcopper plate, engraved with a series of lines 0.0036 deep, 0.004 inchwide, separated 0.0135 on center. The solid dispersion was applied tothe plate, wiped clean with a doctor blade, printed, and dried. The sameengravers plate was then moved over half the spacing of the lines (usingregistration pins); the plate (and the bed of the press) were heated to120 C. (heaters are built right into the press), the hot-melt liquiddispersion was applied to the plate, the plate was wiped clean by aheated doctor blade, and the paper which had already been printed withthe solid dispersion was reprinted with the hot-melt and was immediatelycooled. The hot-melt lines were printed cleanly between the lines of thesolid dispersion.

B. A conventional rotary-gravure press was used. The steel gravureprinting roll was mechanically engraved on a lathe to havecircumferential grooves 0.0135 inch apart on center, 0.0035 inch deep,and 0.0036 inch wide. This roll printed parallel lines in the directionthe paper travelled. The solid reactant was printed first at roomtemperature, and was dried continuously in conventional fashion; thehot-melt liquid dispersion was then printed on a similar roll at 120 C.(the printing roll, ink fountain, and doctor blade were preheated to thedesired temperature). The paper was moved over half the width of theline so that the melt-liquid registered between the dry dispersion. Themelt was allowed to solidify at room temperature before the paper wasrewound. The time for solidification is short enough so that it takesplace in the space on the press usually used to dry inks. A chill rollis not needed, although it can be used.

C. The dispersions were run on the press exactly as in B, but theprinting rolls where photo-engraved with an inverted half-tone patterncontaining dots to the inch,

at 30% tone (i.e., the dots or semi-spherical depressions covered 30% ofthe total roll surface), and a depth of 0.0055 inch at the center. Whileit was convenient to apply both reactants with rolls engraved the sameway, it is equally practical to apply one component with a roll having a40% tone and the second having a 30% or 45% tone, provided the spacingof the half-tone dots (center .to center) is identical on the two rolls,when properly registered, by conventional gravure printing methods.

D. The dispersions were applied as in C, but the rolls werephoto-engraved with an inverted half-tone dot pattern having dots to theinch, at a 35% tone, 0.0045 inch deep. The paper was run through aprinting station (i.e., with a blank smooth roll), and then throughconventional driers; thereafter it was printed with the solid reactantand dried, and with the liquid reactant, at C. and cooled. Because thedot pattern was so fine, registration had to be carried out with extremeac curacy, and the stabilization of the paper by the preprintingoperation was of help in maintaining the necessary registration.

E. A metal plate 0.006 inch thick was perforated by conventionalphoto-engraving techniques with a series of half-tone dots, forming an85 line screen, at 35% tone. This screen was mounted in a conventionalsilk-screen press, and the dry-reactant was screened on paper by forcingthe ink through the holes in the screen by a conventional squeegee, inthe usual stencil (silk-screen) printing operation. After the printswere dry, the screen and a special synthetic polymer squeegee werepreheated to 85 C. and the hot-melt dispersion was applied at 85 C.(instead of 110 C.). This temperature was selected because it produced aviscosity of the melt that was suitable for screen printing.

In all the above examples, the printed sheet had an orange-yellow color.When it was marked with a stylus,

pencil or typewriter, or a letterpress print, a bright blue mark wasformed immediately.

The same solid and liquid reagents have been applied to 20-lb. bondpaper, to newsprint, to super-calendered white paper. As in all printingthe rate of operation of the press, the pressure of the back-up roll,and the viscosity of the reagent inks had to be adjusted to suit thestock being printed just as these adjustments have to be made inconventional ink printing operations.

For commercial production I prefer in general to apply our reagents byprocedure B because this procedure yields the minimum difficulties withregistration (only lateral registration is needed). The roll need not bemechanically engraved. I have used equally well similar rolls engravedwith rows of conventional gravure cells (i.e., rectangular in shape) andwith rows of so-called inverted half-tone shape. I prefer the lattertype of cell, because it can be readily engraved in steel ormagnesium-faced rolls which can be chrome plated or, in the case of themagnesium, anodized, to yield a very long printing life.

Examples-Group II i, parts ii, parts Ferric Sulfate 60 80 Dow Ethocel 10cps 2O 20 Toluene 192 (to produce a viscosity of 60 seconds at 20 C., asmeasured by a No. 2 Zahn Cup). Again, conventional plasticizers may beused if Wanted.

The following liquid reactants were applied:

Parts Parlon S- a chlorinated rubber manufactured by Hercules Powder Co.having a viscosity of 4-7 centiposes at 25 C. in a concentration of 20%in toluene) 35 Diphenylphthalate (other conventional plasticizers may beused) 5 Toluene 60 Igepal CA-630 0.5

Into this solution is dispersed a solution of Ethylene glycol 7 5 Water25 Gallic acid 16 A turbine-type or similar colloid mill is used toattain a stable water-in-oil emulsion.

Parts Cumar V-l (as in Group I examples) 35 Diphenylphthalate 5 DowEthylcellulose, Standard type, 168 cps. viscosi y 2 Igepal CA-63i0 0.5Toluene 60 into which are dispersed, with a colloid mill, a solution ofEthylene glycol 133 Water 131 Gallic acid 32 NaOH 3.3

This dispersion is thixotropic-it is fluid enough to print efiectivelywhen feeding from the colloid mill and may be rendered fluid againsubsequently by active agitation. The presence of the alkali makes thereaction somewhat more effective than without the alkali Other alkaliesmay also be used; the highly hygroscopic nature of the sodium hydroxidehowever is of assistance in retaining equilibrium moisture in theprinted dispersions.

NOTE.Other surface-active agents can be used instead the Igepal CA630.It is one which is effective.

Into this solution was dispersed a separate solution of Parts Gelatin(195 Bloom, 51.5 viscosity) Water u 96.5 Ethylene glycol 85.4 Gallicacid 32 12 of the liquid phase and to assist in forming a gooddispersion.

These reagents were applied in pairs (one solid reagent, one liquid) bythe procedures described under B and C of Example I, except that in thisgroup the liquid reagent was applied at room temperature, like aconventional ink, not as a hot melt, and was dried after printing in theconventional manner.

The paper containing these reactants marked with various types of styliand on a typewriter operated without a ribbon, to yield a black tobrownish-black reactant.

ExamplesGroup III The solid reactant was applied as a ball milleddispersion of Parts Potassium ferrocyanide 9O Ethocel, 1O cps 20 Tolueneto make a viscosity of seconds at 20 C.

as measured by a No. 2 Zahn Cup. The liquid dispersion consisted ofParts Parlon S-5 35 Diphenylphthalate 5 lgcpal CA-63O 0.5 Toluene 60 inwhich was dispersed a solution of Ferric ammonium sulfate 50 Ethyleneglycol 120 Water 80 i.e., a solvent-type ink. This was applied on thepress at room temperature.

Parts Curnar V-l 100 Dibutyl phthalate 10 U.S.P. white mineral oil 0.5

Melted together and cooled to C. then dispersed into it was a hot (95C.) solution of Ferric ammonium sulfate 20 Ethylene glycol 48 Water 32i.e., a hot-melt; this melt was applied at 95 C. on the press.

Both of these combinations were applied by procedures B and C of ExampleI. to yield effective record papers that were white in color and gave ablack record trace. ExamplesGroup IV In Example I if we substitute forthe hot-melt (cumar example given) the following:

Parts Carnauba wax 2O Gum dammar 80 Igepal CA-630 0.5 Ethylene glycol 86Potassium carbonate 27 we have a reactant that does not work withpressure, but does work when melted with a hot stylus.

I need hardly point out that the above examples are merely illustrative.My invention does not reside in having used the cited reactants or anyother of the many reactants reported in the patent and technicalliterature. Any of the well-known reactions may be applied by my processto yield a working product. Whereas in the prior art multiple layers ofthe reactants are piled upon each other, with the well-known drawback ofsuch products, by my process the reactants are kept safely apart butstill sufficiently close to react when the liquid dispersion is brokenby an activating stylus, typewriter key or letterpress type.

It is of course possible to have both reactants applied as liquiddispersions in binders instead of having one reactant solid. In generalhowever it will be obviously better from an economic and practical pointof view to have as many components as possible applied as solids.

The multiplicity of binders used in making printing inks can all beeffectively used in practicing the invention. It will be evident thatthe selection of such a binder will be made first because of the surfaceon which it is to be printed, second because of the solvent to be used,and finally from a cost standpoint. Certainly so far as solid reactantsare concerned practically every known binder that is flexible enough forthe intended b se on which it is to be printed will be adequate for use.In general the weight of binder used will range from twice the weight ofreactant to one-tenth the weight of the reactant. Any conventionalplasticizers may be used with these binders. The solid reactant may beapplied as a hot-melt instead of solution. The necessary change in theformulations to achieve any desired type of binder are well known in theink and coating arts. The spreading of the ink with the particularprinting equipment and web used should not permit the two reactants tomerge during the printing operation. Since this factor varies with theparticular press and paper used, it is not practical to specifynumerically here the exact formulation that should be used in any givenapplication. It will be well within the skill of any ink maker toestablish a suitable formulation in order to produce liquid reactants ina binder that will not spread on any particular specified web.

So far as the liquid reactants are concerned, the primary requirement isthat the binder be readily broken by the inscribing instrumentality andthat the reactant be effectively encapsulated by the binder until it isbroken by pressure or by heat.

I am aware that the invention may be embodied in other specific formswithout departing from the spirit or essential attributes thereof, and Itherefore desire the present embodiment to be considered in all respectsas illustrative and not restrictive, as is in fact clear in severalmatters from the description itself. Reference is to be had to theappended claims to indicate those principles of the inventionexemplified by the particular embodiment described and which I desire tosecure by Letters Patent.

1 claim:

1. The method of making an inscription medium which comprises imprintingon a base with a fluid formulation of a first potentially reactivematerial a two-dimensional array of closely arranged but effectivelyisolated impressions, drying the same to set the impressions, thenprinting in the interstices between the impressions, with a fluidformulation of a second potentially reactive material which if mixedwith the first results in a chromogenetic reaction, a second twodimensional array of impressions closely arranged with but effectivelyisolated from both each other and the impressions of the first array anddrying the second impressions, the density of distribution of theelements of the two arrays taken together being such that at leastseveral of each array are present in any area one sixteenth of an inchsquare.

2. The method of claim 1 wherein the elements of each array formlongitudinal files.

3. The method as set forth in claim 1 wherein the elements of the firstgroup of impressions are solid when set and those of the second compriseliquid droplets dispersed in a binder.

4. The method as set forth in claim 3 wherein the impressions of thefirst group are of such volume that they are of greater altitude thanthose of the second group when both are dried.

5. A material for receiving inscriptions which material is ofmegascopically homogeneous surface texture and tone and comprises a basesheet having individually adherent to the surface thereof the elementsof several twodimensional arrays, each of regularly arranged andrelatively spaced small masses containing at least one potentiallyreactant material, which reactant materials of the masses of the severalarrays, if mixed, will initiate a reaction resulting in a conspicuouschange in appearance, the elements of the arrays respectively being outof register each with each of the others and the elements of each array,and of all the arrays considered as one, being spaced from one anotheron the surface of the base sheet, the individual areas and density ofdistribution of such elements being such that at least several of eachkind are present in any area of the sheet one sixteenth of an inchsquare, the masses being distortable under the influence of aninscribing instrumentality presented to and moving relatively to thematerial along or transversely to its surface so that the material ofthe masses of one array overruns spaces which normally isolate them tomix operatively with the adjacent masses of other arrays to eifectlocalized reaction between the reactant materials with the resultantappearance of a conspicuous inscription.

6. A material as set forth in claim 5 wherein the masses of one arraycontain two ingredients, inert to each other, but one of which promotesthe reaction of the other with the different potentially reactiveingredient in the masses of another array when the masses of the twoarrays are mixed.

7. A material as set forth in claim 5 wherein the masses of at least onearray are formulated from liquid droplets dispersed in a binder.

8. A material as set forth in claim 7 wherein the masses of anotherarray are formulated in solid form and are of greater altitude than themasses which contain liquid droplets.

9. A material as set forth in claim 7 wherein the masses of one arrayare formulated as a dispersion of fine solid particles of potentiallyreactive substance in a binder and the masses of another array areformulated as a dispersion in a binder of fine liquid droplets of asubstance reactive with the last mentioned reactive substance.

10. A material for receiving inscriptions which material is ofmegascopically homogeneous surface texture and tone and comprises a basesheet having individually adherent to the surface thereof the elementsof a first twodimensional array of regularly arranged and relativelyspaced small masses containing at least one potentially reactantmaterial and a second two-dimensional array of regularly arranged andrelatively spaced small masses containing at least one potentiallyreactant material which if mixed with reactant material of the masses inthe first array will initiate a reaction resulting in a conspicuouschange in appearance, the elements of the two arrays respectively beingout of register and the elements of each array, and of the two arraysconsidered as one, being spaced from one another on the surface of thebase sheet, the individual areas and density of distribution of suchelements being such that at least several of each kind are present inany area of the sheet one sixteenth of an inch square, the masses beingdistortable under the influence of an inscribing instrumentalitypresented to and moving relatively to the material along or transverselyto its surface so that the material of the masses of one array overrunsspaces which normally isolate them to mix operatively with the adjacentmasses of the other array to effect localized reaction between thereactant materials with the resultant appearance of a conspicuousinscription.

References Cited in the file of this patent UNITED STATES PATENTS

1. THE METHOD OF MAKING AN INSCRIPTION MEDIUM WHICH COMPRISES IMPRINTINGON A BASE WITH A FLUID FORMULATION OF A FIRST POTENTIALLY REACTIVEMATERIAL A TWO-DIMENSIONAL ARRAY OF CLOSELY ARRANGED BUT EFFECTIVELYISOLATED IMPRESSIONS, DRYING THE SAME TO SET THE IMPRESSIONS, THENPRINTING IN THE INTERSTICES BETWEEN THE IMPRESSIONS, WITH A FLUIDFORMULATION OF A SECOND POTENTIALLY REACTIVE MATERIAL WHICH IF MIXEDWITH THE FIRST RESULTS IN A CHGROMOGENETIC REACTION, A SECOND TWODIMENTIONAL ARRAY OF IMPRESSIONS CLOSELY ARRANGED WITH BUT EFFECTIVELYISOLATED FROM BOTH EACH OTHER AND THE IMPRESSIONS, OF THE FIRSTT ARRAYAND DRYING THE SECOND IMPRESSIONS, THE DENSITY OF DISTRIBUTION OF THEELEMENTS OF THE TWO ARRAYS TAKEN TOGETHER BEING SUCH THAT AT LEASTSEVERAL OF EACH ARRAY ARE PRESENT IN ANY AREA ONE SIXTEENTH OF AN INCHSQUARE.